The Dedication of Agatha Christie

The dedication is often the last thing to be written, right? So it makes sense that these manuscripts did not have dedications when they went into their respective vaults. Poirot investigates published in 1924, Partners in Crime, 1929, The Hound of Death, 1933, The Listerdale Mystery, 1934, and Parker Pride investigates also in 1934. And then finally, Ag of the Christie's Autobiography, which does not feature a dedication was published posthumously. These are dedications that stumped me. I do not know who these people are, and this irks me...I want you to help me figure it out.